After 25 years I'm going to break down and get new sails. Should I buy new battens also or just use my originals? I want to keep my old sail for heavy wind (and I like the blue prism appearance) so one way or the other I'll need a set, just whether to buy new (more $$$) or some old ones.

SRM is right, foam or tapered glass battens will have little effect on a stock Hobie sail. I would consult with the sailmaker if its custom and let it be their decision.Chafe tape and new endcaps are probably all you need.

I would always have a complete set of battens for any sail that you intend to use. Even if infrequently in high winds. Having to change them over just to go sailing is a major hassle, meaning you won't do it. Then you'll end up not using that sail and using your good one in high winds. And getting mud stains over the top three feet.